The philosopher Karl Jaspers introduced the concept of the Axial Age to describe convergent movements in thought that occurred across the Old World from the Greco-Roman to the Indian and Chinese. This period from approximately 8th century to the 3rd century BCE was the documented birth of the study of self. Inscribed more than two millennia ago on the Temple of Apollo at Delphi are the three maxims: know thyself, nothing to excess, and certainty brings insanity. To Plato, these three maxims represented a fundamental truth and an aspirational goal. He stated, “the wise or temperate man…will know himself, and be able to examine what he knows or does not know.” For Plato, wisdom was equivalent to temperance and required self-knowledge. Across the old world but nearly contemporaneously, ancient Indians and Chinese were also focused on the self. They developed meditative practices with a focus on the breath (prana or qi) to glean insight and gain mastery of the self. This pursuit of the self was not just idle philosophical ruminations of ancient philosophers and bored Indian aristocrats living in idyllic gardens, but a deliberate and conscious manifestation of an inherent capacity for self-knowledge and self-awareness. Nearly two millennia later, modern brain sciences are beginning to identify, measure, and quantify these neurospsychological processes.
Two processes that serve these capacities of self-knowledge and self-awareness are termed metacognition and interoception. Metacognition is defined as the ability to reflect on our decision, gauge the uncertainty in the information we receive, and calibrate our confidence on levels of informational uncertainty. It allows for self-questioning, learning, and updating beliefs in the face of conflicting information. It is a higher-level, integrative process that is has neural correlates at the uppermost levels of the prefrontal hierarchy. Interoception is a similar higher-order and integrative cortical process that is associated with the insular cortex and has also access to a broad array of inputs from inside the body and across the brain. It represents sensations as “feelings” or “emotions” and generally serves to optimize energy utilization and maintain homeostasis. In effect, metacognition and interoception are both inward looking, higher-order, and integrated processes that improve our ability to infer causes in an outside world of effects (future essay).
As the concepts of self-knowledge and self-awareness have transitioned from the theoretical to the empirical, from the abstract to the tangible, scientists have identified neural correlates and laboratory based measures to identify and quantify these processes. Metacognition can be quantified by metrics such as metacognitive sensitivity and metacognitive bias. The former describes the accuracy of metacognition – being confident when we are right – and the latter describes how accurately our confidence level is calibrated to the level of uncertainty in the information – being (over)confident in a decision even when the information source is unreliable. Metacognitive sensitivity and metacognitive bias can also be identified in neural networks. The brains of individuals with high metacognition – confident when accurate or doubtful when possibly inaccurate – have an identifiably different functional brain connectivity. Similarly, interoception can also be measured in the laboratory. The deceptively easy sounding task of counting one’s heartbeats has been used as a measure of interoceptive awareness. It has been shown that individuals who are better heartbeat perceivers are not only better at reading their own feelings but also make better decisions based on subtle environmental cues, perform better at tasks of selective and divided attention, and respond more quickly to an intuitive choice.
The Socratic adage to know thyself has been an aspirational life mission since the Axial Age. From the self-evaluating philosophy of the ancient Greeks to the prescriptive ancient Indian meditative practices designed to increase self-awareness, the pursuit of metacognition and interception awareness have been framed as virtuous pursuits. However, I suspect this beginning dated to the Axial Age is just an artifact of the invention of writing and proximity in time. The capacities of metacognition and interoception are seemingly inherent features of the human brain. Self-awareness and self-knowledge with its complements – “other”- awareness and “other”- knowledge (next essay) – are characteristic psychological traits of our 300,000 year old species. They are evolved and developed features of the human brain, and like most neurobiological features, serve adaptive functions, are inherently variable within the population, can be honed by experience, and are prone to errors in evolutionary mismatched environments such as the emergency department (future essay).
1. Know Thyself